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Thin clients should be able to discover all server nodes automatically when connected to any of them, and maintain an up to date list of servers at all times. This behavior should be optionalenabled when ClientConfiguration.PartitionAwarenessEnabled property is true.

Description

Clients can track topology changes: IEP-23 Best Effort Affinity introduced a response header change that sends topology version whenever it changes.

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Client Public API Changes

None.

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When ClientConfiguration.PartitionAwarenessEnabled is true, discovery is enabled as well.

Client Logic

1. Connect to one or more endpoints from ClientConfigurationif (!config.DiscoveryEnabled) return;
2. Perform OP_CLUSTER_GROUP_GET_NODE_ENDPOINTS(-1, -1) to retrieve current topology.
3. Connect to every server from (2) that is not yet connected.
   1. Use node UUID to make sure we don't connect to the same node twice
   2. Verify that node UUID from handshake is equal to node UUID from OP_CLUSTER_GROUP_GET_NODE_ENDPOINTS response: when client and server are in different subnets, there can be a mismatch. The node can even belong to a different cluster. Drop the connection in case of a mismatch. 
4. For every response to any operation, compare topology version from the header to the topology version from (2). When it changes, request updated topology with OP_CLUSTER_GROUP_GET_NODE_ENDPOINTS(oldVer, newVer).
5. Connect to newly discovered servers, remove connections to removed servers
6. GOTO (4)

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